The present invention relates to a method and machine for manufacturing a composite hockey stick shaft, and to the hockey stick shaft made therefrom. More particularly, the present invention relates to a double pressing method and machine for manufacturing a laminated hockey stick shaft having graphite and fiberglass reinforcement, and to the hockey stick shaft made therefrom.
It is known in the art that hockey sticks have traditionally been manufactured from wood. The elongated shaft and blade portions of the hockey stick were both constructed of wood and were joined with one another through various processes to form a single, integral unit. The traditional wooden hockey stick has set the standard for weight, feel, and load transfer, and hockey players have long preferred wooden shafts.
It is also known in the art that during the course of a hockey game, a hockey stick is subjected to high stresses, which often result in fracture or breakage of the stick shaft. Additionally, when a wooden hockey stick brakes, it tends to splinter which can be hazardous. Consequently, various attempts have been made throughout the years to improve the durability of hockey sticks without sacrificing the characteristics of weight, feel, and flexibility that are desirable in a hockey stick. As a result, ice hockey sticks have changed from a plain wooden stick having a straight blade and shaft to a significantly improved stick having a curved blade and shaft reinforced with composite materials.
It is known in the art that a laminated hockey stick is made of an ordinary hard wood hockey stick onto which thin layers of reinforcing material are glued over each side of the hockey stick shaft and shank portion. Laminated hockey sticks have been proven to be superior to their solid wood counterparts in order to prevent shaft breakage. Known in the art are laminated hockey sticks made with one reinforcing material such as fiberglass, graphite or the like and an appropriate resin used to glue the laminate onto the core.
It is also known in the art that the mechanical properties of laminated hockey sticks will vary depending on the selected reinforcing material and the type of resin used. Graphite rovings do not absorb polyester resin. A carbon/polyester matrix does not benefit fully from the higher modulus of elasticity of graphite because the filaments remain dry. If one breaks this type of laminate, one will see that the rovings remain flexible, proving that they are not an integral part of the matrix. This means that they are not contributing as much to the rigidity of the finished laminate. In addition, when using polyester resin, the bond between the graphite and the wood core is very poor.
It is also known in the art of making laminated hockey shaft sticks that the traditional polyester process does not control the position of individual rovings, treating the entire group as a unit. There is an increased risk of having nothing but resin in certain portions of the core. Without fibers, the resin chips and cracks upon impact. In addition, there is no control over the distribution of rovings over the laminate cross section.
It is also known that for a same sample core, the average laminate thickness is 0.040xe2x80x3 (approx. 0.1016 cm) with polyester resin, versus 0.0025xe2x80x3 (approx. 0.00635 cm) with vinyl ester resin. The finished shaft with polyester is 0.83xe2x80x3 (approx. 2.1082 cm) thick versus 0.79xe2x80x3 (approx. 2.0066 cm) with vinyl ester. The industry trend is towards a demand for slimmer shafts. Furthermore, for the traditional polyester process, the size of the bath is limited since the polyester resin is not refrigerated. On a press with two lengths of sticks, one portion of the laminate soaks in resin during the entire pressing cycle or longer. The rest simply passes through, for an immersion time of a few seconds. The weight percent of resin in the soaked section is much higher, and cannot be removed through wringing, so a portion of the laminate is thicker and heavier than the rest.
It is also known that the traditional polyester process often requires viscosity control additives. Fillers such as micro-bubbles are added to increase the viscosity of polyester. This is done to reduce leakage of resin from the molds, which must be scraped off later. This reduces the rate of resin penetration in the rovings, even for fiberglass.
Finally, it is also known in the art that laminated hockey sticks are made using a single pressing process wherein the first laminate is glued by applying pressure to the unlaminated side of the core. The load is transferred through the core to the laminate, which is trapped between the core and the mold surface. This means that one side of the core is pressed by a metal plate before it is glued to a laminate. The pores of the wood on this side are smoothed by this, reducing the bond quality when the core is eventually turned over. The result is that one laminate will have a better bond than the other. This can be proven by peeling off cold pressings, and verifying the amount of wood that comes off in the process. Also, in single pressing, one side can be allowed to cool before the other is pressed. The contraction of the laminate will curve the shaft to one side.
Therefore, there is a need to provide a method and a machine for making hockey sticks shafts, which enable to control the position of the individual rovings. There is also a need to provide a method and a machine for making hockey sticks shafts, which enable to treat both sides of a stick symmetrically, so that the bond quality is equal for the top and bottom laminates. Furthermore, there is a need for a hockey stick shaft having improved structural characteristics which lead to improved performance.
The present invention provides a double pressing method and machine for producing a linear product having a core with two opposite surfaces and outer laminates, and a linear product made therefrom which satisfy each of the above mentioned needs.
More particularly, a first object of the invention is to provide a double pressing method and machine for manufacturing a hockey stick shaft having a core with two opposite surfaces and outer laminates by simultaneously pressing a laminate of graphite rovings positioned between fiberglass rovings onto each opposite surface of the hockey stick core.
A second object of the present invention is to provide a hockey stick shaft having a core with two opposite surfaces, each of the surfaces being provided with a laminate comprising fiberglass rovings along each longitudinal surface edge and graphite rovings between the fiberglass rovings.
According to the invention, there is provided a double pressing method for producing a linear product having a core with two opposite surfaces and outer laminates, said method comprising the steps of:
a) providing a plurality of rovings;
b) guiding said rovings through guide means;
c) soaking said rovings in a liquid bath;
d) wringing excess liquid from said rovings;
e) positioning an upper set of wetted rovings under an upper mold cavity and a lower set of wetted rovings over a lower mold cavity;
f) inserting said core between the upper set and lower set of wetted rovings;
g) moving the upper mold cavity and the lower mold cavity towards each other so as to simultaneously press said upper and lower sets of rovings onto the core; and
h) moving the upper mold cavity and the lower mold cavity away from each other so as to remove the resulting linear product.
Also according to the invention, there is provided a machine for double pressing a linear product having a core with two opposite surfaces and outer laminates, said machine comprising:
feeding means for feeding a plurality of rovings;
guiding means for guiding said rovings;
soaking means for soaking said rovings;
wringing means for wringing said rovings;
a double pressing mold having an upper mold cavity and a lower mold cavity;
separating means for separating said rovings into an upper set of wetted rovings and a lower set of wetted rovings;
positioning means for positioning the upper set of wetted rovings under the upper mold cavity and the lower set of wetted rovings over the lower mold cavity;
insertion means for inserting said core between the upper set and lower set of wetted rovings;
pressing means for moving the upper mold cavity and the lower mold cavity towards each other so as to simultaneously press said upper and lower set of rovings onto the core;
ejection means for moving the upper mold cavity and the lower mold cavity away from each other so as to remove the resulting linear product.
Also according to the invention, there is provided a hockey stick shaft comprising an inner core and outer laminates, the inner core comprising a pair of opposite surfaces, each surface being provided with longitudinal surface grooves and longitudinal edge grooves; characterized in that each opposite surface is covered by one of said outer laminates and each outer laminate comprises graphite rovings positioned between fiberglass rovings.